1. Field of the Invention
The present invention relates to a laser processing system.
2. Description of the Related Art
In laser processing systems, it is known that a laser processing machine capable of operating along an inherent control axis, such as orthogonal three axes of a machine tool or a rotation axis of a manipulator, is provided. This type of laser processing system is generally provided with an axis driving section (including a servo-amplifier and a servomotor) for driving the control axis of the laser processing machine, a laser oscillator for supplying a laser beam to the laser processing machine, a control unit for controlling the axis driving section and the laser oscillator, and other peripheral devices.
In the above conventional laser processing system, the control unit is usually connected to the axis driving section, the laser oscillator and the other desired peripheral devices, by using mutually different interfaces. The control unit sends a motion command to the servo-amplifier of the desired axis driving section so as to operate the servomotor, at a predetermined command cycle (such as a interpolation cycle in a numerical control) in accordance with a given laser processing program, and drives the desired control axis so as to shift, along a designated path, a table on which a material to be processed is mounted or a processing nozzle for emitting a laser beam. At the same time, the control unit sends a command regarding various output conditions, such as an emission, a halting, a peak power, a frequency, etc., of a laser beam, to the laser oscillator, at a command cycle usually identical to the cycle of the axis motion command, in accordance with the laser processing program. Thus, the laser oscillator supplies a laser beam of a desired power to the laser processing machine at a desired timing during the operation of the laser processing machine, so as to make the laser processing machine execute laser processing.
In the control unit, motion command data (referred to as motion data in the present application) adapted to be sent to the servo-amplifier and output-condition command data (referred to as laser output-condition data, in the present application) adapted to be sent to the laser oscillator are simultaneously prepared on the basis of the given laser processing program. However, there usually are differences in transfer cycles (i.e., inherent transfer timings) and transfer speeds, between an interface connected to the servo-amplifier and an interface connected to the laser oscillator, both provided in the control unit, so that a time lag arises between the time when the servo-amplifier receives the command and the time when the laser oscillator receives the command. The time lag in association with the data transfer may deteriorate a laser processing accuracy.
For example, in some cases, in order to decrease the cycle time of a laser processing, a desired laser processing is carried out by repeating the emission and halting of a laser beam while operating the laser processing machine at an approximately constant speed. In this case, there is a concern about the fact that a starting point and an ending point of an actual laser processing on the material to be processed is deviated from a target position, due to the above-described time lag in relation to the data transfer. Further, the time of changing a laser output condition (such as a starting or ending of a laser oscillation) designated in the processing program does not necessarily coincide with the above-described command cycle in relation to the data transmission, and, in some cases, the change of the laser output condition is commanded at a timing deviated from the command cycle. In this case, the laser oscillator cannot change the laser output condition until a next command cycle starts, which is subsequent to the cycle in which the change of the laser output condition is commanded in the data received from the control unit, so that the laser oscillator executes the change the laser output condition after a certain delay from the command timing. As a result, there is also a concern about the fact that an actual laser processing area on the material to be processed includes more or less errors relative to a designated processing area (such as a positional deviation of a starting or ending point). The processing errors in the actual processing area tend to become larger when a laser processing speed (i.e., the moving speed of the laser processing machine) increases.
Japanese Unexamined Patent Publication (Kokai) No. 2004-167549 (JP-A-2004-167549) discloses a laser processing machine configured to make it possible to change a laser output condition at a designated timing, without waiting for the start of the subsequent command cycle, in the case where the time of changing the laser output condition in a laser processing program does not coincide with a command cycle of a data transmission. The laser processing machine is configured to calculate a time, on the laser processing program, from the start of a command cycle (or an interpolation cycle), including a changing command of a laser output condition, to the issuance of the command for changing the laser output condition, and, at an instant when the calculated time is spent from the start of the command cycle, to actually command the change of the laser output condition. With this arrangement, it is possible to eliminate a processing error in the actual processing area due to the delay in changing of the laser output condition.
As described above, in order to perform a high-precision processing in the laser processing machine, it is desired to accurately switch or change the various output conditions, such as the emission, the halting, the peak power, the frequency, etc., of a laser beam at a target position, even when the laser processing machine is continuously operating. However, in the conventional laser processing system, a processing error may arise in the actual processing area due to the time lag in association with the data transfer for the axis driving section and for the laser oscillator. The processing error due to the time lag relating to the data transfer is not so serious in a processing speed range in a general or conventional laser processing machine. However, due to a recent development in a laser processing technique or a servo technique, the processing speed of the laser processing machine is improved remarkably and, therefore, the deterioration in a processing accuracy due to the above-described factors becomes more significant.
In order to minimize the processing error due to the time lag in the data transfer, it is effective to shorten a data transfer cycle or increase a data transfer speed, at the individual interfaces in the control unit, respectively connected to the axis driving section and the laser oscillator, which may, however, increase the cost of building the system. On the other hand, the technique described in JP-A-2004-167549 makes it possible to change the laser output condition at a designated timing, without waiting for the subsequent command cycle, in the case where the time of changing the laser output condition in the laser processing program does not coincide with the command cycle of the data transmission. However, based on this technique, it is also difficult to solve the problem of time lag in the data transfer due to the difference of the interfaces in the control unit.